Such sources, in which an electroluminophor powder is located in an electric field created between two or more electrodes, are known. However, all of these devices suffer from a fundamental disadvantage which is inherent in the method of preparation of all cable-like EL sources: as the EL layer is applied to the cable core (whether conductive or insulating) by a continuous process of dip-coating, the EL particle/binder mixture must be a liquid of a fairly low viscosity, which is achieved by adding a suitable solvent. Yet once the EL layer is applied, this solvent, as is the way of solvents, evaporates and leaves behind a layer that is full of air-containing pores. These pores greatly reduce the electrical capacity of the EL sources and, thereby, their brightness.
A further drawback of the prior art EL sources resides in the fact that the above-mentioned air-filled pores constitute an optical discontinuity in the EL layer, causing further, substantial light losses due to total internal reflection at the binder/air interface, as well as through dispersion by the irregular wall surfaces of these air bubbles.